As UnderGroundTech said, You will have to find out what model laptop You have.
Then, You will have to find the manufacturer's web site (from a different computer) and find the WiFi driver(s) for that laptop. It is possible you will need to install other drivers as well, like a chipset driver before installing the WiFi driver.
Copy all those drivers from the other PC onto a USB flash drive and then copy them onto Your laptop.
Install the drivers. This will involve a number of reboots.
Finally, if you get the WiFi drivers installed correctly, You get to set up all Your WiFi networks again.